Method for receiving downlink control information by ue in wireless communication system, and apparatus for same

ABSTRACT

The present invention relates to a method for receiving control information by a UE in a wireless communication system, and an apparatus for same. More specifically, the method includes a step of receiving reconfiguration downlink control information (DCI), wherein the reconfiguration DCI includes a plurality of reconfigurations relating to a UE group including the UE and is configured so as to be received on the basis of a radio network temporary identifier (RNTI) defined for the reconfiguration DCI.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more particularly, to a method for receiving downlink controlinformation by a user equipment in a wireless communication system, andan apparatus for the same.

BACKGROUND ART

A 3rd generation partnership project long term evolution (3GPP LTE)(hereinafter, referred to as ‘LTE’) communication system which is anexample of a wireless communication system to which the presentinvention can be applied will be described in brief.

FIG. 1 is a diagram illustrating a network structure of an EvolvedUniversal Mobile Telecommunications System (E-UMTS) which is an exampleof a wireless communication system. The E-UMTS is an evolved version ofthe conventional UMTS, and its basic standardization is in progressunder the 3rd Generation Partnership Project (3GPP). The E-UMTS may bereferred to as a Long Term Evolution (LTE) system. Details of thetechnical specifications of the UMTS and E-UMTS may be understood withreference to Release 7 and Release 8 of “3rd Generation PartnershipProject; Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), basestations (eNode B; eNB), and an Access Gateway (AG) which is located atan end of a network (E-UTRAN) and connected to an external network. Thebase stations may simultaneously transmit multiple data streams for abroadcast service, a multicast service and/or a unicast service.

One or more cells exist for one base station. One cell is set to one ofbandwidths of 1.44, 3, 5, 10, 15 and 20 MHz to provide a downlink oruplink transport service to several user equipments. Different cells maybe set to provide different bandwidths. Also, one base station controlsdata transmission and reception for a plurality of user equipments. Thebase station transmits downlink (DL) scheduling information of downlinkdata to the corresponding user equipment to notify the correspondinguser equipment of time and frequency domains to which data will betransmitted and information related to encoding, data size, and hybridautomatic repeat and request (HARQ). Also, the base station transmitsuplink (UL) scheduling information of uplink data to the correspondinguser equipment to notify the corresponding user equipment of time andfrequency domains that can be used by the corresponding user equipment,and information related to encoding, data size, and HARQ. An interfacefor transmitting user traffic or control traffic may be used between thebase stations. A Core Network (CN) may include the AG and a network nodeor the like for user registration of the user equipment. The AG managesmobility of the user equipment on a Tracking Area (TA) basis, whereinone TA includes a plurality of cells.

Although the wireless communication technology developed based on WCDMAhas been evolved into LTE, request and expectation of users andproviders have continued to increase. Also, since another wirelessaccess technology is being continuously developed, new evolution of thewireless communication technology will be required for competitivenessin the future. In this respect, reduction of cost per bit, increase ofavailable service, use of adaptable frequency band, simple structure andopen type interface, proper power consumption of the user equipment,etc. are required.

DISCLOSURE Technical Problem

An object of the present invention devised to solve the problem lies ina method for receiving downlink control information by a user equipmentin a wireless communication system, and an apparatus for the same.

Objects of the present invention are not limited to the aforementionedobject, and other objects of the present invention which are notmentioned above will become apparent to those having ordinary skill inthe art upon examination of the following.

Technical Solution

The object of the present invention can be achieved by providing amethod for receiving control information by a user equipment (UE) in awireless communication system, including receiving reconfigurationdownlink control information (reconfiguration DCI), wherein thereconfiguration DCI includes a plurality of reconfigurations about a UEgroup including the UE, and is set to be received based on a radionetwork temporary identifier (RNTI).

The reconfiguration DCI may be set to be transmitted through a commonsearch space (CSS) of a primary cell (PCell).

The RNTI defined for the reconfiguration DCI may be identicallyconfigured for the UE group. Preferably, the RNTI defined for thereconfiguration DCI may be configured through UE-specific radio resourcecontrol (RRC) signaling.

When the number of bits for the plurality of reconfigurations is lessthan the number of bits constituting the reconfiguration DCI, unusedbits of the bits constituting the reconfiguration DCI may be set to aspecific value.

The specific value may be considered as a virtual cyclic redundancycheck (virtual CRC) by the UE.

The number of the reconfigurations may be indicated through higher layersignaling or physical layer signaling.

The number of bits constituting the reconfiguration DCI may be indicatedthrough higher layer signaling or physical layer signaling.

The locations of the reconfigurations may be set to differ from eachother. Further, information about the locations of the reconfigurationsmay be indicated through UE-specific signaling.

In another aspect of the present invention, provided herein is a userequipment for receiving control information in a wireless communicationsystem, including a radio frequency unit; and a processor, wherein theprocessor is configured to receive reconfiguration downlink controlinformation (reconfiguration DCI), wherein the reconfiguration DCIincludes a plurality of reconfigurations about a UE group including theUE, and is set to be received based on a radio network temporaryidentifier (RNTI).

Advantageous Effects

According to embodiments of the present invention, a downlink controlsignal for a user equipment may be efficiently received in a wirelesscommunication system.

Effects that can be obtained from the present invention are not limitedto the aforementioned effect, and other effects may be clearlyunderstood by those skilled in the art from the descriptions givenbelow.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates an architecture of an E-UMTS network of a wirelesscommunication system.

FIG. 2 illustrates a control plane and user plane of a radio interfaceprotocol between a user equipment based on the 3GPP wireless accessnetwork standard and E-UTRAN.

FIG. 3 illustrates physical channels used in a 3GPP LTE system and ageneral method for transmitting a signal using the same.

FIG. 4 illustrates the structure of a radio frame used in an LTE system.

FIG. 5 shows a resource grid of a downlink slot.

FIG. 6 exemplarily shows a downlink subframe structure.

FIG. 7 shows resource units used to configure a downlink control channelin an LTE system.

FIG. 8 illustrates a carrier aggregation (CA) communication system.

FIG. 9 illustrates a scheduling operation in the case where a pluralityof carriers is aggregated.

FIG. 10 illustrates an EPDCCH and a PDSCH scheduled by the EPDCCH.

FIG. 11 shows an example of CoMP operation.

FIG. 12 illustrates dynamically switching the usage of a radio resourcein the environment of a TDD system.

FIG. 13 shows a format defined for the purpose of transmission ofchange-of-use information (e.g., a change-of-use indicator) according toan embodiment of the present invention.

FIGS. 14 to 16 illustrate association configuration betweenchange-of-use information about multiple cells transmitted according toa predefined format and multiple cell-specific information statesaccording to an embodiment of the present invention.

FIG. 17 illustrates new DCI for UL-DL reconfiguration according to anembodiment of the present invention.

FIG. 18 illustrates a method for transmitting and receiving a signalaccording to one embodiment of the present invention.

FIG. 19 exemplarily shows a base station and a user equipment which areapplicable to an embodiment of the present invention.

BEST MODE

The following technology may be used for various wireless accesstechnologies such as CDMA (code division multiple access), FDMA(frequency division multiple access), TDMA (time division multipleaccess), OFDMA (orthogonal frequency division multiple access), andSC-FDMA (single carrier frequency division multiple access). The CDMAmay be implemented by the radio technology such as UTRA (universalterrestrial radio access) or CDMA2000. The TDMA may be implemented bythe radio technology such as global system for mobile communications(GSM)/general packet radio service (GPRS)/enhanced data rates for GSMevolution (EDGE). The OFDMA may be implemented by the radio technologysuch as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, andevolved UTRA (E-UTRA). The UTRA is a part of a universal mobiletelecommunications system (UMTS). A 3rd generation partnership projectlong term evolution (3GPP LTE) is a part of an evolved UMTS (E-UMTS)that uses E-UTRA, and adopts OFDMA in a downlink and SC-FDMA in anuplink. LTE-advanced (LTE-A) is an evolved version of the 3GPP LTE.

For clarification of the description, although the following embodimentswill be described based on the 3GPP LTE/LTE-A, it is to be understoodthat the technical spirits of the present invention are not limited tothe 3GPP LTE/LTE-A. Also, specific terminologies hereinafter used in theembodiments of the present invention are provided to assistunderstanding of the present invention, and various modifications may bemade in the specific terminologies within the range that they do notdepart from technical spirits of the present invention.

FIG. 2 is a diagram illustrating structures of a control plane and auser plane of a radio interface protocol between a user equipment andE-UTRAN based on the 3GPP radio access network standard. The controlplane means a passageway where control messages are transmitted, whereinthe control messages are used by the user equipment and the network tomanage call. The user plane means a passageway where data generated inan application layer, for example, voice data or Internet packet dataare transmitted.

A physical layer as the first layer provides an information transferservice to an upper layer using a physical channel. The physical layeris connected to a medium access control (MAC) layer via a transportchannel, wherein the medium access control layer is located above thephysical layer. Data are transferred between the medium access controllayer and the physical layer via the transport channel. Data aretransferred between one physical layer of a transmitting side and theother physical layer of a receiving side via the physical channel. Thephysical channel uses time and frequency as radio resources. In moredetail, the physical channel is modulated in accordance with anorthogonal frequency division multiple access (OFDMA) scheme in adownlink, and is modulated in accordance with a single carrier frequencydivision multiple access (SC-FDMA) scheme in an uplink.

A medium access control (MAC) layer of the second layer provides aservice to a radio link control (RLC) layer above the MAC layer via alogical channel. The RLC layer of the second layer supports reliabledata transmission. The RLC layer may be implemented as a functionalblock inside the MAC layer. In order to effectively transmit data usingIP packets such as IPv4 or IPv6 within a radio interface having a narrowbandwidth, a packet data convergence protocol (PDCP) layer of the secondlayer performs header compression to reduce the size of unnecessarycontrol information.

A radio resource control (RRC) layer located on the lowest part of thethird layer is defined in the control plane only. The RRC layer isassociated with configuration, re-configuration and release of radiobearers (‘RBs’) to be in charge of controlling the logical, transportand physical channels. In this case, the RB means a service provided bythe second layer for the data transfer between the user equipment andthe network. To this end, the RRC layers of the user equipment and thenetwork exchange RRC message with each other. If the RRC layer of theuser equipment is RRC connected with the RRC layer of the network, theuser equipment is in an RRC connected mode. If not so, the userequipment is in an RRC idle mode. A non-access stratum (NAS) layerlocated above the RRC layer performs functions such as sessionmanagement and mobility management.

One cell constituting an eNB is set to one of bandwidths of 1.4, 3.5, 5,10, 15, and 20 MHz and provides a downlink or uplink transmissionservice to several user equipments. At this time, different cells may beset to provide different bandwidths.

As downlink transport channels carrying data from the network to theuser equipment, there are provided a broadcast channel (BCH) carryingsystem information, a paging channel (PCH) carrying paging message, anda downlink shared channel (SCH) carrying user traffic or controlmessages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted via the downlink SCH or anadditional downlink multicast channel (MCH). Meanwhile, as uplinktransport channels carrying data from the user equipment to the network,there are provided a random access channel (RACH) carrying an initialcontrol message and an uplink shared channel (UL-SCH) carrying usertraffic or control message. As logical channels located above thetransport channels and mapped with the transport channels, there areprovided a broadcast control channel (BCCH), a paging control channel(PCCH), a common control channel (CCCH), a multicast control channel(MCCH), and a multicast traffic channel (MTCH).

FIG. 3 is a diagram illustrating physical channels used in a 3GPP LTEsystem and a general method for transmitting a signal using the physicalchannels.

The user equipment performs initial cell search such as synchronizingwith the base station when it newly enters a cell or the power is turnedon at step S301. To this end, the user equipment synchronizes with thebase station by receiving a primary synchronization channel (P-SCH) anda secondary synchronization channel (S-SCH) from the base station, andacquires information such as cell ID, etc. Afterwards, the userequipment may acquire broadcast information within the cell by receivinga physical broadcast channel (PBCH) from the base station. Meanwhile,the user equipment may identify a downlink channel status by receiving adownlink reference signal (DL RS) at the initial cell search step.

The user equipment which has finished the initial cell search mayacquire more detailed system information by receiving a physicaldownlink shared channel (PDSCH) in accordance with a physical downlinkcontrol channel (PDCCH) and information carried in the PDCCH at stepS302.

Afterwards, the user equipment may perform a random access procedure(RACH) such as steps S303 to S306 to complete access to the basestation. To this end, the user equipment may transmit a preamble througha physical random access channel (PRACH) (S303), and may receive aresponse message to the preamble through the PDCCH and the PDSCHcorresponding to the PDCCH (S304). In case of a contention based RACH,the user equipment may perform a contention resolution procedure such astransmission (S305) of additional physical random access channel andreception (S306) of the physical downlink control channel and thephysical downlink shared channel corresponding to the physical downlinkcontrol channel.

The user equipment which has performed the aforementioned steps mayreceive the physical downlink control channel (PDCCH)/physical downlinkshared channel (PDSCH) (S307) and transmit a physical uplink sharedchannel (PUSCH) and a physical uplink control channel (PUCCH) (S308), asa general procedure of transmitting uplink/downlink signals. Controlinformation transmitted from the user equipment to the base station willbe referred to as uplink control information (UCI). The UCI includesHARQ ACK/NACK (Hybrid Automatic Repeat and reQuestAcknowledgement/Negative-ACK), SR (Scheduling Request), CSI (ChannelState Information), etc. In this specification, the HARQ ACK/NACK willbe referred to as HARQ-ACK or ACK/NACK (A/N). The HARQ-ACK includes atleast one of positive ACK (simply, referred to as ACK), negative ACK(NACK), DTX and NACK/DTX. The CSI includes CQI (Channel QualityIndicator), PMI (Precoding Matrix Indicator), RI (Rank Indication), etc.Although the UCI is generally transmitted through the PUCCH, it may betransmitted through the PUSCH if control information and traffic datashould be transmitted at the same time. Also, the user equipment maynon-periodically transmit the UCI through the PUSCH in accordance withrequest/command of the network.

FIG. 4 is a diagram illustrating a structure of a radio frame used in anLTE system.

Referring to FIG. 4, in a cellular OFDM radio packet communicationsystem, uplink/downlink data packet transmission is performed in a unitof subframe, wherein one subframe is defined by a given time intervalthat includes a plurality of OFDM symbols. The 3GPP LTE standardsupports a type 1 radio frame structure applicable to frequency divisionduplex (FDD) and a type 2 radio frame structure applicable to timedivision duplex (TDD).

FIG. 4( a) is a diagram illustrating a structure of a type 1 radioframe. The downlink radio frame includes 10 subframes, each of whichincludes two slots in a time domain. A time required to transmit onesubframe will be referred to as a transmission time interval (TTI). Forexample, one subframe may have a length of 1 ms, and one slot may have alength of 0.5 ms. One slot includes a plurality of OFDM symbols in atime domain and a plurality of resource blocks (RB) in a frequencydomain. Since the 3GPP LTE system uses OFDM in a downlink, OFDM symbolsrepresent one symbol interval. The OFDM symbol may be referred to asSC-FDMA symbol or symbol interval. The resource block (RB) as a resourceallocation unit may include a plurality of continuous subcarriers in oneslot.

The number of OFDM symbols included in one slot may be varied dependingon configuration of a cyclic prefix (CP). Examples of the CP include anextended CP and a normal CP. For example, if the OFDM symbols areconfigured by the normal CP, the number of OFDM symbols included in oneslot may be 7. If the OFDM symbols are configured by the extended CP,since the length of one OFDM symbol is increased, the number of OFDMsymbols included in one slot is smaller than that of OFDM symbols incase of the normal CP. For example, in case of the extended CP, thenumber of OFDM symbols included in one slot may be 6. If a channel stateis unstable like the case where the user equipment moves at high speed,the extended CP may be used to reduce inter-symbol interference.

If the normal CP is used, since one slot includes seven OFDM symbols,one subframe includes 14 OFDM symbols. At this time, first maximum threeOFDM symbols of each subframe may be allocated to a physical downlinkcontrol channel (PDCCH), and the other OFDM symbols may be allocated toa physical downlink shared channel (PDSCH).

FIG. 4( b) is a diagram illustrating a structure of a type 2 radioframe. The type 2 radio frame includes two half frames, each of whichincludes four general subframes, which include two slots, and a specialsubframe which includes a downlink pilot time slot (DwPTS), a guardperiod (GP), and an uplink pilot time slot (UpPTS).

In the special subframe, the DwPTS is used for initial cell search,synchronization or channel estimation at the user equipment. The UpPTSis used for channel estimation at the base station and uplinktransmission synchronization of the user equipment. In other words, theDwPTS is used for downlink transmission, whereas the UpPTS is used foruplink transmission. Especially, the UpPTS is used for PRACH preamble orSRS transmission. Also, the guard period is to remove interferenceoccurring in the uplink due to multipath delay of downlink signalsbetween the uplink and the downlink.

Configuration of the special subframe is defined in the current 3GPPstandard document as illustrated in Table 1 below.

Table 1 illustrates the DwPTS and the UpPTS in case ofT_(s)=1/(15000×2048), and the other region is configured for the guardperiod.

TABLE 1 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Normal Extended Normal Extended Special subframecyclic prefix cyclic prefix cyclic prefix cyclic prefix configurationDwPTS in uplink in uplink DwPTS in uplink in uplink 0  6592 · T_(s) 2192· T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 ·T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600· T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592· T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) 12800 · T_(s) 8 24144 · T_(s) — — — 9 13168 ·T_(s) — — —

In the meantime, the structure of the type 2 radio frame, that is,uplink/downlink configuration (UL/DL configuration) in the TDD system isas illustrated in Table 2 below.

TABLE 2 Uplink- Downlink- downlink to-Uplink config- Switch-pointSubframe number uration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U UD S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D DD D D 6 5 ms D S U U U D S U U D

In the above Table 2, D means the downlink subframe, U means the uplinksubframe, and S means the special subframe. Also, Table 2 alsoillustrates a downlink-uplink switching period in the uplink/downlinksubframe configuration of each system.

The structure of the aforementioned radio frame is only exemplary, andvarious modifications may be made in the number of subframes included inthe radio frame, the number of slots included in the subframe, or thenumber of symbols included in the slot.

FIG. 5 is a diagram illustrating a resource grid of a downlink slot.

Referring to FIG. 5, the downlink slot includes a plurality of N^(DL)_(symb) OFDM symbols in a time domain and a plurality of N^(DL) _(RB)resource blocks in a frequency domain. Since each resource blockincludes N^(RB) _(sc) subcarriers, the downlink slot includes N^(DL)_(RB)×N^(RB) _(sc) subcarriers in the frequency domain. Although FIG. 5illustrates that the downlink slot includes seven OFDM symbols and theresource block includes twelve subcarriers, it is to be understood thatthe downlink slot and the resource block are not limited to the exampleof FIG. 5. For example, the number of OFDM symbols included in thedownlink slot may be varied depending on the length of the CP.

Each element on the resource grid will be referred to as a resourceelement (RE). One resource element is indicated by one OFDM symbol indexand one subcarrier index. One RB includes

N_(symb)^(DL) × N_(sc)^(RB)

number of resource elements. The number N^(DL) _(RB) of resource blocksincluded in the downlink slot depends on a downlink transmissionbandwidth configured in the cell.

FIG. 6 is a diagram illustrating a structure of a downlink subframe.

Referring to FIG. 6, maximum three (four) OFDM symbols located at thefront of the first slot of the subframe correspond to a control regionto which a control channel is allocated. The other OFDM symbolscorrespond to a data region to which a physical downlink shared channel(PDSCH) is allocated. Examples of downlink control channels used in theLTE system include a Physical Control Format Indicator Channel (PCFICH),a Physical Downlink Control Channel (PDCCH), and a Physical Hybrid ARQIndicator Channel (PHICH). The PCFICH is transmitted from the first OFDMsymbol of the subframe, and carries information on the number of OFDMsymbols used for transmission of the control channel within thesubframe. The PHICH carries HARQ ACK/NACK (Hybrid Automatic RepeatreQuest acknowledgement/negative-acknowledgement) signals in response touplink transmission.

The control information transmitted through the PDCCH will be referredto as downlink control information (DCI). The DCI includes resourceallocation information for a user equipment or user equipment group. Forexample, the DCI includes uplink/downlink scheduling information, uplinktransmission (Tx) power control command, etc.

The PDCCH may include transport format and resource allocationinformation of a downlink shared channel (DL-SCH), transport format andresource allocation information of an uplink shared channel (UL-SCH),paging information on a paging channel (PCH), system information on theDL-SCH, resource allocation information of upper layer control messagesuch as random access response transmitted on the PDSCH, a set oftransmission (Tx) power control commands of individual user equipments(UEs) within a random user equipment group, transmission (Tx) powercontrol command, and activity indication information of voice overInternet protocol (VoIP). A plurality of PDCCHs may be transmittedwithin the control region. The user equipment may monitor the pluralityof PDCCHs. The PDCCH is transmitted on aggregation of one or a pluralityof continuous control channel elements (CCEs). The CCE is a logicallocation unit used to provide the PDCCH with a coding rate based onthe status of a radio channel. The CCE corresponds to a plurality ofresource element groups (REGs). The format of the PDCCH and the numberof available bits of the PDCCH are determined depending on the number ofCCEs. The base station determines a PDCCH format depending on the DCIwhich will be transmitted to the user equipment, and attaches cyclicredundancy check (CRC) to the control information. The CRC is maskedwith an identifier (for example, radio network temporary identifier(RNTI)) depending on usage of the PDCCH or owner of the PDCCH. Forexample, if the PDCCH is for a specific user equipment, the CRC may bemasked with cell-RNTI (C-RNTI) of the corresponding user equipment. Ifthe PDCCH is for a paging message, the CRC may be masked with a pagingidentifier (for example, paging-RNTI (P-RNTI)). If the PDCCH is forsystem information (in more detail, system information block (SIB)), theCRC may be masked with system information RNTI (SI-RNTI). If the PDCCHis for a random access response, the CRC may be masked with a randomaccess RNTI (RA-RNTI).

FIG. 7 shows resource units used to configure a downlink control channelin an LTE system. In particular, FIG. 7( a) illustrates a case where abase station has one or two transmit antennas, and FIG. 7( b)illustrates a case where a base station has four transmit antennas. Inthese two cases, only a reference signal (RS) pattern changes accordingto the number of transmit antennas, and the same method for configuringa resource unit related to a control channel is applied.

Referring to FIG. 7, the basic resource unit of a downlink controlchannel is a resource element group (REG). Except for the case of an RS,an REG consists of four neighboring resource elements (REs). Each REG isindicated by bold lines in the figure. A PCFICH includes 4 REGs and aPHICH includes 3 REGs. A PDCCH is configured in a unit of controlchannel elements (CCEs), and one CCE includes 9 REGs.

A UE is configured to check M^((L))(≧L) CCEs which are consecutive orarranged according to a specific rule, in order to check whether or nota PDCCH consisting of L CCEs is transmitted thereto. The value of Lwhich the UE must consider in receiving the PDCCH may be greater than 1.CCE sets that the UE must check to receive a PDCCH are called a searchspace. For example, an LTE system defines the search space as shown inTable 3 below.

TABLE 3 Search space S_(k) ^((L)) Number of PDCCH Type Aggregation levelL Size [in CCEs] candidates M^((L)) UE-specific 1 6 6 2 12 6 4 8 2 8 162 Common 4 16 4 8 16 2

Herein, the CCE aggregation level L denotes the number of CCEsconstituting a PDCCH, S_(k) ^((L)) denotes the search space of CCEaggregation level L, M^((L)) denotes the number of candidate PDCCHs thatneed to be monitored in the search space of the aggregation level L.

The search space may be divided into a UE-specific search space, inwhich only a specific UE is allowed to perform access, and a commonsearch space, in which all UEs in a cell are allowed to perform access.A UE monitors common search spaces corresponding to CCE aggregationlevels 4 and 8 and UE-specific search spaces corresponding to CCEaggregation levels 1, 2, 4 and 8. A common search space may overlap aUE-specific search space.

In a PDCCH search space assigned to a UE for each CCE aggregation levelvalue, the location of the first CCE (a CCE having the lowest index)changes in each subframe depending on the UE. This is called PDCCHsearch space hashing.

CCEs may be distributed over a system band. More specifically, aplurality of logically consecutive CCEs may be input to an interleaver,which functions to mix the input CCEs on an REG-by-REG basis. Thereby,frequency/time resources constituting one CCE may be physicallydistributed in the whole frequency/time domain within a control regionof a subframe. In other words, interleaving is performed on theREG-by-REG basis although a control channel is configured on theCCE-by-CCE basis. Thereby, frequency diversity and interferencerandomization gain may be maximized.

FIG. 8 illustrates a carrier aggregation (CA) communication system.

Referring to FIG. 8, a plurality of UL/DL component carriers (CCs) maybe collected to support a wider UL/DL bandwidth. The term “componentcarrier (CC)” may be replaced with another equivalent term (e.g.,carrier, cell, etc.). CCs may or may not be adjacent to each other inthe frequency domain. The bandwidth of each CC may be independentlydetermined. Asymmetric carrier aggregation in which the number of UL CCsdiffers from that of DL CCs is also possible. Meanwhile, controlinformation may be configured to be transmitted and received through aspecific CC. This specific CC may be referred to as a primary CC (or ananchor CC), and the other CCs may be referred to as secondary CCs.

When cross-carrier scheduling (or cross-CC scheduling) is applied, aPDCCH for DL assignment may be transmitted on DL CC#0, and acorresponding PDSCH may be transmitted on DL CC#2. To ensure cross-CCscheduling, a carrier indicator field (CIF) may be introduced. In thePDCCH, presence of CIF may be semi-statically and UE-specifically (or UEgroup-specifically) indicated through higher layer signaling (e.g., RRCsignaling). A baseline for PDCCH transmission is summarized below.

-   -   CIF Disabled: A PDCCH on a DL CC is assigned a PDSCH resource on        the same DL CC or a PUSCH resource on one linked UL CC.    -   No CIF    -   Identical to LTE PDCCH structure (the same coding, same        CCE-based resource mapping) and DCI format    -   CIF Enabled: A PDCCH on a DL CC can be assigned a PDSCH or PUSCH        resource on a specific DL/UL CC among a plurality of aggregated        DL/UL CCs, using a CIF    -   An extended LTE DCI format having a CIF        -   The CIF (when configured) is a fixed x-bit field (e.g., x=3)        -   The location of the CIF (when configured) is fixed            irrespective of the size of the DCI format.    -   Reusing the LTE PDCCH structure (the same coding and same        CCE-based resource mapping)

When a CIF is present, a base station may assign a PDCCH monitoring DLCC set to lower BD complexity on the UE. The PDCCH monitoring DL CC setincludes at least one DL CC which is a part of all aggregated DL CCs,and the UE detects/decodes a PDCCH only on the at least one DL CC. Thatis, if the base station schedules a PDSCH/PUSCH for the UE, the PDCCH istransmitted through only the PDCCH monitoring DL CC set. The PDCCHmonitoring DL CC set may be configured in a UE-specific,UE-group-specific or cell-specific manner. The term “PDCCH monitoring DLCC” may be replaced with another equivalent term such as “monitoringcarrier” and “monitoring cell”. In addition, a CC aggregated for the UEmay be expressed as an equivalent term such as “serving CC,” “servingcarrier,” and “serving cell”.

FIG. 9 illustrates a scheduling operation in the case where a pluralityof carriers is aggregated. It is assumed that 3 DL CCs have beenaggregated. It is also assumed that DL CC A is configured as a PDCCHmonitoring DL CC. DL CCs A to C may be referred to as serving CCs,serving carriers, serving cells, or the like. If the CIF is disabled,each DL CC may transmit only a PDCCH for scheduling the PDSCH thereofwithout a CIF according to the LTE PDCCH configuration. On the otherhand, if the CIF is enabled by UE-specific (or UE-group-specific orcell-specific) higher layer signaling, not only a PDCCH for schedulingthe PDSCH of DL CC A but also a PDCCH for scheduling the PDSCH ofanother CC may be transmitted on DL CC A (a monitoring DL CC) using theCIF. In this case, a PDCCH is not transmitted on DL CC B/C, which is notconfigured as a PDCCH monitoring DL CC. Accordingly, DL CC A (amonitoring DL CC) must include a PDCCH search space related to DL CC A,a PDCCH search space related to DL CC B and a PDCCH search space relatedto DL CC C. In this specification, it is assumed that a PDCCH searchspace is defined for each carrier.

As described above, LTE-A considers using the CIF in a PDCCH to performcross-CC scheduling. Whether the CIF is used (namely, a cross-CCscheduling mode or non-cross-CC scheduling mode is supported) andswitching between the modes may be semi-statically/UE-specificallyconfigured through RRC signaling. After being subjected to the RRCsignaling process, the UE may recognize whether the CIF is used in aPDCCH that is to be scheduled therefor.

FIG. 10 illustrates an EPDCCH and a PDSCH scheduled by the EPDCCH.

Referring to FIG. 10, for the EPDCCH, a part of the PDSCH region fortransmitting data may be generally defined and used. A UE must performblind decoding to detect presence of an EPDCCH thereof. The EPDCCHperforms the same scheduling operation (i.e., controlling a PDSCH and aPUSCH) as performed by the legacy PDCCH, but may increase complexitywhen the number of UEs accessing a node such as the RRH since the numberof EPDCCHs assigned in the PDSCH region increases and thus the number oftimes of blind decoding which a UE needs to perform increases.

Hereinafter, cooperative multipoint transmission/reception (CoMP) willbe described.

Systems after LTE-A consider introducing a method to improve systemperformance by enabling cooperation among multiple cells. This method iscalled cooperative multipoint transmission/reception (CoMP). CoMP refersto a communication scheme in which two or more base stations, accesspoints or cells cooperate in order to smoothly communicate with aspecific UE. In the present invention, the terms base station, accesspoint, and cell may have the same meaning.

Generally, in a multi-cell environment where the frequency reuse factoris 1, performance and average sector throughput of a UE positioned at acell boundary may be lowered due to inter-cell interference (ICI). Inorder to attenuate such ICI, the legacy LTE system uses a simple passivetechnique such as fractional frequency reuse (FFR) through UE-specificpower control to ensure that a UE positioned at the cell boundaryexhibits proper throughput performance in an environment where the UE issubjected to interference. However, it may be more preferable toattenuate ICI or reuse ICI as a signal desired by the UE than to lowerfrequency resource use per cell. To achieve this object, a CoMPtransmission technique may be applied.

FIG. 11 shows an example of CoMP operation. Referring to FIG. 11, awireless communication system includes a plurality of bass stations BS1,BS2 and BS3 and a UE which perform CoMP. the base stations BS1, BS2 andBS3 performing CoMP may cooperate, thereby efficiently transmitting datato the UE. CoMP may be divided into two techniques depending on whetheror not data is transmitted from a base station performing CoMP:

-   -   CoMP joint processing (CoMP-JP)    -   CoMP cooperative scheduling (CoMP-CS)/cooperative beamforming        (CB)

In CoMP-JP, base stations performing CoMP transmit data to one UEsimultaneously, and the UE improves reception performance by combiningsignals from the base stations. That is, according to the CoMP-JPtechnique, each point (base station) in a CoMP cooperation unit may usedata. The CoMP cooperation unit refers to a set of base stations usedfor a cooperative transmission scheme. The JP scheme may be divided intojoint transmission and dynamic cell selection.

Joint transmission refers to a technique of simultaneously transmittingPDSCHs from a plurality of transmission points (a part or the entiretyof a CoMP cooperation unit). That is, a plurality of transmission pointsmay transmit data to a single UE simultaneously. With the jointtransmission technique, the quality of a received signal may becoherently or non-coherently improved, and interference with other UEsmay be actively eliminated.

Dynamic cell selection is a technique of transmitting a PDSCH from onetransmission point (of a CoMP cooperation unit) at a time. That is, onetransmission point transmits data to a single UE at a specific time,while the other transmission points in the CoMP cooperation unit do nottransmit data to the UE at this time. A transmission point to transmitdata to a UE may be dynamically selected.

On the other hand, when CoMP-CS is used, data is transmitted from onebase station to a UE at a certain moment, and scheduling or beamformingis performed such that interference with the other base stations isminimized. That is, when the CS/CB technique is used, CoMP cooperationunits may cooperatively perform beamforming for data transmission to asingle UE. While data is transmitted to the UE only from a serving cell,user scheduling/beamforming may be determined through coordination amongcells in the CoMP cooperation unit.

In the case of uplink, CoMP reception refers to reception of a signaltransmitted through cooperation among a plurality of geographicallyseparated transmission points. CoMP schemes applicable to uplink may beclassified into joint reception (JR) and coordinatedscheduling/beamforming (CS/CB).

JR refers to a technique of a plurality of reception points receiving asignal transmitted through a PUSCH. The CS/CB refers to a technique ofonly one point receiving a PUSCH, and user scheduling/beamforming isdetermined by coordination among the cells of a CoMP unit.

Hereinafter, interference between multiple cells will be described.

When coverages of two base stations (e.g., BS#1 and BS#2) partiallyoverlap as in the case where the two base stations are disposed adjacentto each other, a UE served by one base station may be subjected tointerference of a strong DL signal from the other base station. Ifinter-cell interference occurs as above, the interference may beattenuated through inter-cell cooperative signaling between the two basestations. In the description of various embodiments of the presentinvention given below, it is assumed that signal transmission andreception are smoothly performed between two base stations interferingwith each other. For example, it is assumed that there is awired/wireless link (e.g., a backhaul link or Un interface) on whichtransmission conditions such as a transmission bandwidth or time delaybetween the base stations are good and thus the reliability oftransmission and reception of a cooperative signal between the basestations is high. It may also be assumed that time synchronizations isestablished between the two base stations within a tolerance (e.g., theboundaries of DL subframes of two base stations interfering with eachother are aligned) or that an offset between subframe boundaries of thetwo base stations is clearly recognized by the two base stations.

Referring back to FIG. 11, BS#1 may be a macro eNB serving a wide areawith a high transmit power, and BS#2 may be a micro eNB (e.g., a picoeNB) serving a narrow area with a low transmit power. As illustrated inFIG. 11, if a UE located in a cell boundary area of BS#2 and served byBS#2 is subjected to strong interference from BS#1, effectivecommunication may not be performed without proper inter-cellcooperation.

In particular, inter-cell interference is very likely to occur when alarge number of UEs is allowed to be connected to BS#2 serving as amicro eNB having low power in order to distribute service load of BS#1serving as a macro eNB. For example, when the UE attempts to select aserving base station, the UE may calculate and compare receive powers ofDL signals from the base stations by adding a predetermined coordinationvalue (a bias value) to the receive power from the micro eNB withoutadding a coordination value to the receive power from the macro eNB.Then, the UE may select a base station providing the highest DL transmitpower as a serving base station. Thereby, a larger number of UEs may beallowed to be connected to the micro eNB. The micro eNB may be selectedas a serving base station even though the DL signal received by the UEfrom the macro eNB is much stronger than the DL signal from the microeNB. In this case, the UEs connected to the micro eNB may experiencestrong interference from the macro eNB. Thereby, UEs located at thecoverage boundary of the micro eNB may not correctly operate due tostrong interference from the macro eNB if separate inter-cellcooperation is not provided.

To ensure effective operation even if inter-cell interference exists,proper cooperation should be established between two base stationsapplying inter-cell interference to each other, and a signal forenabling such cooperation may be transmitted and received via a linkbetween the two base stations. In this case, if inter-cell interferenceoccurs between the macro eNB and the micro eNB, the macro eNB maycontrol inter-cell cooperative operation, and the micro eNB may properlyoperate according to a cooperative signal delivered from the macro eNB.

The inter-cell interference situation described above is simplyillustrative. It is apparent that the embodiments described in thepresent invention are also applied to other situations where inter-cellinterference occurs (for example, when inter-cell interference occursbetween a CSG type HeNB and an OSG type macro eNB, when the micro eNBinterferes with the macro eNB, or when inter-cell interference existsbetween micro eNBs or between macro eNBs).

FIG. 12 illustrates a case where a specific cell changes a part of ULresources (i.e., UL SFs) for use in DL communication in a TDD system asdownlink load increases in the system.

In FIG. 12, a UL/DL configuration established through an SIB is assumedto be UL/DL #1 (i.e., DSUUDDSUUD), UL SF #(n+3) and UL SF #(n+8) arechanged for downlink communication through a predefined signal (e.g., aphysical/higher layer signal or a system information signal).

The present invention proposes a method for efficientlytransmitting/receiving change-of-use information (e.g., a change-of-useindicator) when multiple cells dynamically change use of a radioresource according to the system load applied thereto as describedabove.

Herein, the change-of-use information (e.g., a change-of-use indicator)may be transmitted through i) a physical downlink control channel(PDCCH) and/or ii) an enhanced PDCCH (EPDCCH) that is transmitted in thephysical downlink shared channel (PDSCH) region, and/or iii) a physicalbroadcast channel (PBCH) (e.g., MIB), and/or iv) a higher layer signal(e.g., RRC, MAC), and/or v) a system information block (SIB).

The PDSCH region is defined as a region consisting of the OFDM symbolsconfiguring a subframe except a few leading OFDM symbols of the subframewhich are used for (conventional) PDCCH transmission. The presentinvention is also applicable to the case where there are no OFDM symbolswhich are used for PDCCH transmission and thus all OFDM symbols of asubframe are designated and used as a PDSCH region.

Hereinafter, for simplicity, the proposed method will be described basedon the 3GPP LTE system. However, the proposed method is also applicableto systems other than the 3GPP LTE system.

Embodiments of the present invention are applicable in the case where aresource on a specific cell (or a component carrier (CC)) is dynamicallychanged according to the load applied to the system in an environmentwhere a carrier aggregation (CA) technique is employed.

Embodiments of the present invention are also applicable in the casewhere use of a radio resource is dynamically changed in a TDD system,FDD system or TDD/FDD-aggregated system.

Additionally, embodiments of the present invention are also applicablein the case where change-of-use information (e.g., a change-of-useindicator) is transmitted in the form of i) a UE-specific signal, and/orii) a cell-specific signal and/or iii) a UE group-specific signal.Herein, the change-of-use information may be transmitted through theUE-specific search space (USS) and/or a common search space (CSS).

For example, transmitting change-of-use information (e.g., achange-of-use indicator) through the CSS with the CA technique appliedmay be interpreted as meaning that the change-of-use information isreceived in the form of a predefined DCI format through a primary cell(or a primary CC) on which the CSS is valid. In another example, if theCA technique is applied, and the change-of-use information is set to betransmitted through a PDCCH (or predefined DCI) in the CSS (wherein thePDCCH (or predefined DCI) is decoded (or detected) through, for example,a (UE group-specific or UE-specific) RNTI which is additionallypredefined), change-of-use information about the secondary cells (orsecondary CCs) may also be transmitted through the PDCCH (or predefinedDCI) related to transmission of the change-of-use informationtransmitted in the CSS on the primary cell (or primary CC).

Hereinafter, for simplicity of description, it is assumed that cellsdynamically change use of an existing resource according to load appliedthereto in a TDD system environment.

Description is given below of configuration of the proposedchange-of-use information (e.g., a change-of-use indicator). Accordingto an embodiment of the present invention, the change-of-use informationmay be set to be signaled to a UE by a base station using a predefinedformat. For example, change-of-use information may be transmitted over aphysical control channel, physical data channel, higher layer signal, orsystem information transmission channel, and a UE may receive thechange-of-use information based on a predefined RNTI (e.g., a new RNTIdefined to receive the change-of-use information or an existing RNTIused to receive a specific channel (information)).

Further, change-of-use information (e.g., a change-of-use indicator) maybe transmitted based on a predefined periodicity, or the samechange-of-use information (e.g., the same change-of-use indicator) maybe repeatedly transmitted a predetermined number of times based on aspecific periodicity or within a specific period such that theinformation is transmitted with a high reliability.

The predefined format may be defined such that change-of-use information(e.g., change-of-use indicators) about not only one specific servingcell (or serving transmission point (hereinafter, serving TP)) but alsomultiple cells (or transmission points (hereinafter, TPs)) istransmitted. Such format may be particularly effective in signalingchange-of-use information (e.g., change-of-use indicators) aboutmultiple cells to a specific UE (e.g., CoMP UE) when cells (or TPs)participating in CoMP operation dynamically change use of a radioresource.

The format may also be applied to transmit change-of-use information(e.g., change-of-use indicators) about multiple cells (e.g., SCells) ina situation in which the multiple cells (or CCs) are configured throughthe CA technique. For example, information (e.g., UL-DL(re)configuration) about use of subframes for multiple cells (TPs) maybe set to be signaled in the form of UL-DL configuration information ona serving cell (e.g., a PCell or scheduling cell) and an offset valuefor the UL-DL configuration of the serving cell. In the case where UL-DLconfiguration information about two cells (TPs) is transmitted, if UL-DLconfiguration #0 (i.e., DSUUUDSUUU) and an offset value of 2 for theserving cell (or serving TP) are signaled, the UL-DL configuration forthe other cells (or the other TPs) may be considered to be UL-DLconfiguration #2 (i.e., DSUDDDSUDD). For cells (or TPs) whose subframeusage information is not changed, specific predefined bits (or UL-DLconfiguration information about the cells or TPs on an SIB) may betransmitted. Further, the number of the specific bits may be smallerthan or equal to that of the bits needed to signal changed usageinformation on a specific cell (or specific TP).

Accordingly, a UE receiving the change-of-use information mayeffectively perform, for each cell, i) channel state measurement (e.g.,RRM/RLM/CSI), ii) monitoring of a control channel (e.g., anEPDCCH/PDCCH), or iii) transmission/reception of a data channel (e.g.,PSUCH, PDSCH), based on a predefined rule. The subframes in which the UEperforms measurement of channel state information (e.g., RRM/RLM/CSI)for individual cells or the subframes in which the UE monitors a controlchannel (e.g., EPDCCH/PDCCH) may be limited to i) a subframe set whicheach cell uses for downlink, ii) a subframe set which cellsparticipating in CoMP operation use for downlink in common, or iii) apredefined (DL) subframe set (e.g., a DL subframe set (i.e., SF #0, #1,#5, #6) use of which cannot be changed through transmission ofPSS/SSS/PBCH).

The change-of-use information (e.g., change-of-use indicator) about therespective cells (or TPs) may include not only information (e.g., UL-DL(re)configuration) about use of the subframes but also at least one ofi) physical/virtual cell (or TP) identifier information, ii) specialsubframe configuration information, iii) identifier information aboutUEs for which dynamic change is applied, iv) group identifierinformation about a specific UE group for which dynamic change isapplied, v) dynamic change configuration information about individualcells (or TPs), vi) QCL configuration information about individual cells(or TPs), vii) non-zero power CSI-RS configuration information, viii)zero power CSI-RS configuration information, ix) IMR configurationinformation, x) information defined in association with a PQI field.Herein, the dynamic change configuration information about individualcells (or TPs) may include, for example, information indicating whetheror not a specific reference signal (e.g., CRS, CSI-RS) is transmitted insubframes whose usage has changed and/or TM configuration information(or transmission technique configuration information). In addition, theinformation defined in association with the PQI field may include atleast a part or all of i) the number of CRS antenna ports for PDSCH REmapping (crs-PortsCount-r11) information, ii) CRS frequency shift forPDSCH RE mapping (crs-FreqShift-r11) information, iii) MBSFN subframeconfiguration for PDSCH RE mapping information(mbsfn-SubframeConfigList-r11), iv) zero power CSI-RS resourceconfiguration for PDSCH RE mapping information (csi-RS-ConfigZPId-r11),v) PDSCH starting position for PDSCH RE mapping information(pdsch-Start-r11), vi) CSI-RS resource that is quasi co-located with thePDSCH antenna port information (qcl-CSI-RS-ConfigNZPId-r11), and vii)configuration information related to RE mapping of EPDCCH and EPDCCHantenna port Quasi co-location.

FIG. 13 shows a format defined for the purpose of transmission ofchange-of-use information (e.g., a change-of-use indicator) according toan embodiment of the present invention. While FIG. 13 illustrates aformat for transmission of change-of-use information about arbitrarycells, a format for transmission of change-of-use information aboutarbitrary TPs may also be applied in the same manner.

In FIG. 13, it is assumed that change-of-use information about M cells(or TPs) is transmitted through the format of the change-of-useinformation. Corresponding information (i.e., information about thenumber of cells (or TPs) about which the change-of-use information iscurrently transmitted through one piece of change-of-use information orinformation about the number of fields which are used for transmissionof change-of-use information among the fields in one change-of-useinformation format) may be transmitted to a UE by a base station throughone of a physical control channel (e.g., EPDCCH/PDCCH), a physical datachannel (e.g., PDSCH), a higher layer signal (e.g., RRC/MAC) and asystem information transmission channel (e.g., PBCH/SIB/Paging).Alternatively, in the case where change-of-use information (e.g.,change-of-use indicators) about multiple cells (or TPs) is transmittedbased on a predefined format, the base station may pre-deliver specificinformation states about multiple cells (or TPs) to the UE throughsignaling (e.g., RRC signaling) and establish a configuration such thatthe UE may recognize cell-specific information of a cell (or TP-specificinformation of a TP) associated with change-of-use information (e.g., achange-of-use indicator) according to a predefined rule.

Further, in the case where the multiple cells (or CCs) are configuredthrough the CA technique, the same operation as above may be performedwhen change-of-use information (e.g., change-of-use indicators) aboutmultiple cells is transmitted.

For example, cell-specific (or TP-specific) information may includeinformation about at least one of i) a physical/virtual cell (or TP)identifier associated with change-of-use information (e.g., achange-of-use indicator) at a specific position in a predefined format,ii) QCL configuration of the cell (or TP), iii) non-zero power CSI-RSconfiguration of the cell (or TP), iv) zero power CSI-RS configurationof the cell (or TP), v) IMR configuration zero power CSI-RSconfiguration of the cell (or TP), vi) PDSCH/(E)PDCCH rate-matchingconfiguration of the cell (or TP) and vii) information defined inassociation with a PQI field. Herein, the information defined inassociation with the PQI field may include, for example, at least a partor all of i) the number of CRS antenna ports for PDSCH RE mapping(crs-PortsCount-r11) information, ii) CRS frequency shift for PDSCH REmapping (crs-FreqShift-r11) information, iii) MBSFN subframeconfiguration for PDSCH RE mapping information(mbsfn-SubframeConfigList-r11), iv) zero power CSI-RS resourceconfiguration for PDSCH RE mapping information (csi-RS- ConfigZPId-r11),v) PDSCH starting position for PDSCH RE mapping information(pdsch-Start-r11), vi) CSI-RS resource that is Quasi co-located with thePDSCH antenna ports information (qcl-CSI-RS-ConfigNZPId-r11), vii)configuration information related to RE mapping of EPDCCH and EPDCCHantenna port Quasi co-location.

In addition, a relationship between cell-specific (or TP-Specific)information states defined through change-of-use information (e.g.,change-of-use indicators) in a predefined format and additionalsignaling (e.g., RRC signaling) may be determined based on a predefinedrule. For example, M pieces of change-of-use information in thepredefined format are transmitted, the base station may configure orsignal M cell-specific (or TP-specific) information states for the UEsuch that change-of-use information is sequentially mapped one-to-one tocell-specific (or TP-specific) information. That is, the base stationmay cause the J-th change-of-use information to be associated with theJ-th cell-specific (or TP-specific) information state.

In the case where change-of-use information (e.g., change-of-useindicators) about M (a natural number) cells (or TPs) is transmittedbased on a predefined format, the number of pieces of cell-specific (orTP-specific) information delivered to the UE by the base station may bedefined as being greater than or equal to M. Herein, if change-of-useinformation items (e.g., change-of-use indicators) about M cells (orTPs) are transmitted based on a predefined format, but cell-specific (orTP-specific) information signaled to the UE by the base station isdefined by information states the number of which is less than M, thismeans that some cells (or TPs) share the same cell-specific (orTP-specific) information. Some cells (or TPs) may share the samecell-specific information even in the case where the number of pieces ofchange-of-use information substantially transmitted at a time is greaterthan that of pieces of cell-specific (or TP-specific) informationsignaled to the UE by the base station.

On the other hand, if change-of-use information (e.g., change-of-useindicators) about M cells (or TPs) is transmitted based on a predefinedformat, the number of pieces cell-specific (or TP-specific) informationsignaled to the UE by the base station may be defined as being greaterthan M. This means that some cells (or TPs) share the same change-of-useinformation (or UL-DL configuration) (which is similar to, for example,a case in which a cell clustering interference mitigation scheme isapplied). This is because non-zero power CSI-RS configurationinformation for each cell (or TP) may be differently configured for somecells to ensure RRM/RLM/CSI measurement of the UE according to each cell(or TP) or be differently configured for all cells, and specificnon-zero power CSI-RS information may implicitly indicate one specificcell (or TP), in the case where the some cells (or TPs) share the samechange-of-use information.

That is, if the number of pieces of cell-specific (or TP-specific)information signaled to the UE by the base station through a predefinedformat is greater than that of pieces of change-of-use information(e.g., M), this means that the number of pieces of non-zero power CSI-RSinformation associated with the pieces of configured cell-specific (orTP-specific) information the number of which is relatively large isgreater than that of pieces of change-of-use information. Moreover, thismeans that the number of cells (or TPs) distinguished by differentpieces of non-zero power CSI-RS configuration information is larger thanthat of pieces of change-of-use information, and ultimately means thatsome cells (or TPs) share the same change-of-use information (or UL-DLconfiguration).

In addition, the scheme of defining the number of pieces ofchange-of-use information substantially transmitted at a time as beinggreater than M when change-of-use information about M cells istransmitted based on a predefined format as described above may also beapplied when the number of pieces of change-of-use information (e.g.,change-of-use indicators) substantially transmitted at a time is lessthan that of pieces of cell-specific (or TP-specific) informationsignaled to the UE by the base station.

A field (or bit) indicating state information corresponding tocell-specific (or TP-specific) information associated with specificchange-of-use information (e.g., change-of-use indicator) in apredefined format through which change-of-use information (e.g.,change-of-use indicators) about multiple cells (or TPs) may beadditionally defined. Such additional definition for the change-of-useinformation is effective in (flexibly) designating a relation (e.g., aone-to-many relation or many-to-one relation) between two kinds ofinformation when the number of pieces of change-of-use informationtransmitted through a predefined format is not equal to that ofcell-specific (or TP-specific) information states defined throughadditional signaling (e.g., RRC signaling).

Additionally, a rule under which the base station pre-signals multiplecell-specific (or TP-specific) information states to the UE and causescell-specific (or TP-specific) information of a cell (or TP) associatedwith change-of-use information (e.g., a change-of-use indicator) to berecognized according to a predefined rule may be interpreted as definingUL-DL configuration information according to each PQI state (PQI fieldvalue) or as defining UL-DL configuration information according to eachPQI state (PQI field k) and each QCL information.

In addition, in the case where a format predefined for transmittingchange-of-use information (e.g., change-of-use indicator) has a fixedlength L_(Total) (the format may carry, for example, N fixed pieces ofUL-DL (re)configuration information (wherein N is a natural number) andhave (L_(Total)-N*S) extra bits (wherein, S denotes bits (e.g., 3 bits)defined to express one UL-DL configuration information (related to onespecific cell (or TP)))), if the number of cells/TPs/CCs for whichsubframe usage is actually changed is less than N, i) an unused UL-DL(re)configuration information field, ii) a UL-DL (re)configurationinformation field which is not associated with a cell/TP/CC-specificinformation state, or iii) a UL-DL (re)configuration information fieldwhich is not associated with a specific cell/TP/CC may be produced alongwith the (L_(Total)-N*S) extra bits.

In addition, in the case where a format predefined for transmittingchange-of-use information (e.g., change-of-use indicator) (i.e., aformat having length L_(Total)) can carry N fixed UL-DL(re)configuration information (wherein, N is a natural number) (e.g.,LTotal is N*S, wherein S denotes bits (e.g., 3 bits) defined to expressone UL-DL configuration information item (related to one specific cell(or TP))), if the number of cells/TPs/CCs for which subframe usage isactually changed is less than N, i) an unused UL-DL (re)configurationinformation field, ii) a UL-DL (re)configuration information field whichis not associated with a cell/TP/CC-specific information state, or iii)a UL-DL (re)configuration information field which is not associated witha specific cell/TP/CC may be produced. For example, when a formatpredefined for transmission of change-of-use information (e.g., achange-of-use indicator) has length L_(Total) corresponding to 8 bitsand UL-DL (re)configuration information about a one specific cell (orTP) is defined in 3 bits, if change-of-use information (e.g.,change-of-use indicator) about two (i.e., M is set to 2) cells (or TPs)is transmitted in the format related to transmission of thechange-of-use information (e.g., change-of-use indicator), the totalnumber of bits not actually used in the format is 2. In another example,when a format predefined for transmission of change-of-use information(e.g., a change-of-use indicator) has length L_(Total) corresponding to8 bits, and UL-DL (re)configuration information about one specific cell(or TP) is defined in 3 bits, if change-of-use information (e.g., achange-of-use indicator) about one cell (or TP) (M is set to 1) istransmitted in the format related to transmission of the change-of-useinformation (e.g., change-of-use indicator), the number of bits whichare not actually used in the format is 5.

Therefore, according to this embodiment, UL-DL configuration informationon an SIB of a cell/TP/CC whose usage information is not changed may beinserted in i) an unused UL-DL (re)configuration information field, ii)a UL-DL (re)configuration information field which is not associated witha cell/TP/CC-specific information state, iii) a UL-DL (re)configurationinformation field which is not associated with a specific cell/TP/CC, oriv) the (L_(Total)-N*S) extra bits.

Alternatively, a predefined specific bit (or value) or information on apredefined specific state may be inserted in i) an unused UL-DL(re)configuration information field, ii) a UL-DL (re)configurationinformation field which is not associated with a cell/TP/CC-specificinformation state, iii) a UL-DL (re)configuration information fieldwhich is not associated with a specific cell/TP/CC, or iv) the(L_(Total)-N*S) extra bits. Accordingly, causing a predefined specificbit/value or information on a predefined specific state to be insertedin an unused field and/or the (L_(Total)-N*S) extra bits in a formatindicating change-of-use information may be viewed as meaning that theUE uses (interprets) the field and/or (L_(Total)-N*S) extra bits aselements for zero padding or virtual CRC.

The length of bits (a field) used for zero padding or virtual CRC in apredefined format used for transmission of change-of-use information(e.g., a change-of-use indicator) may be derived from “the entire lengthof the format L_(Total)-FLOOR (the entire length of the formatL_(Total)/a bit length S defined to express one piece of UL-DLconfiguration information (related to one specific cell (or TP)))*thebit length S defined to express one piece of UL-DL configurationinformation (related to one specific cell (or TP))”. Herein, floor(X)may be defined as an integer which is not greater than X (i.e., adiscarding operation). That is, the “the entire length of the formatL_(Total)-FLOOR (the entire length of the format L_(Total)/a bit lengthS defined to express one piece of UL-DL configuration information(related to one specific cell (or TP)))*the bit length S defined toexpress one piece of UL-DL configuration information (related to onespecific cell (or TP))” including the last bit (or LSB) in the formatare used in reverse order for zero padding or virtual CRC. Forreference, when a specific UE group monitors a format related totransmission of one common change-of-use information item (e.g., achange-of-use indicator) (based on one common RNTI), the rule describedabove may ensure that bits (or a field) having a common length (orposition) are used for zero padding or virtual CRC, regardless of thenumber of cells to which individual UEs (belonging to the UE group)apply the CA technique.

Alternatively, UL-DL configuration information on an SIB of a servingcell/TP/CC (e.g., PCell, scheduling Cell) transmitting the format may beinserted in i) an unused UL-DL (re)configuration information field, ii)a UL-DL (re)configuration information field which is not associated witha cell/TP/CC-specific information state, iii) a UL-DL (re)configurationinformation field which is not associated with a specific cell/TP/CC, oriv) the (L_(Total)-N*S) extra bits.

In addition, the UE may apply specific change-of-use information (e.g.,a specific change-of-use indicator) to a cell/TP/CC which is QCL withnon-zero power CSI-RS configuration/CRS configuration associated withthe specific change-of-use information (namely, with respect to PDSCH inview of blind decoding for downlink) when the UE receives thechange-of-use information. That is, the UE MAY derive a cell/TP/CC towhich the specific change-of-use information (e.g., change-of-useindicator) is applied from QCL information of a specific referencesignal. Herein, the QCL information of the specific reference signal maybe interpreted as being an indicator indicating a cell/TP/CC to whichthe specific change-of-use information is applied.

Herein, non-zero power CSI-RS/CRS configuration information associatedwith the specific change-of-use information (e.g., change-of-useindicator) may be configured through a cell-specific (or TP-specific)information state which is defined through additional signaling. Inparticular, to ensure RRM/RLM/CSI measurement of the UE for respectivecells (or TPs), all or some non-zero power CSI-RS configurationinformation for the respective cells (or TPs) may be differentlyconfigured. Accordingly, the specific non-zero power CSI-RS informationmay implicitly indicate one specific cell (or TP). Additionally, theaforementioned operation is also applicable to PUSCH if a virtual cellID takes the form of a DM-RS scrambling seed.

As another example, causing the UE to apply specific change-of-useinformation (e.g., a specific change-of-use indicator) to a cell/TP/CCwhich is QCL with non-zero power CSI-RS configuration/CRS configurationassociated with the information when the UE receives the specificchange-of-use information (e.g., change-of-use indicator) may beinterpreted as defining UL-DL configuration information for each QCLinformation or for each QCL information and each PQI state (PQI fieldvalue).

FIGS. 14 to 16 illustrate association configuration betweenchange-of-use information (e.g., change-of-use indicators) aboutmultiple cells transmitted according to a predefined format and multiplecell-specific (or TP-specific) information states defined through anadditional signal according to an embodiment of the present invention.

In FIG. 14, it is assumed that change-of-use information about threecells (TPs) is transmitted through a predefined format and that a basestation signals three cell-specific (or TP-specific) information statesto a UE.

Referring to FIG. 14, UL-DL (re)configuration information about cell (orTP) #A in a predefined format, UL-DL (re)configuration information aboutcell (or TP) #B, UL-DL (re)configuration information about cell (or TP)#C are configured to be associated with cell-specific (or TP-specific)information state #0, cell-specific (or TP-specific) information state#1 and cell-specific (or TP-specific) information state #2 respectivelythrough sequential one-to-one mapping.

In FIG. 15, it is assumed that change-of-use information about threecells (TPs) is transmitted through a predefined format and that a basestation signals two cell-specific (or TP-specific) information states toa UE. That is, the figure illustrates a case where one cell-specific (orTP-specific) information state is applied to a plurality of cells (orTPs) or a plurality of change-of-use information items.

In FIG. 15, for UL-DL (re)configuration information about cell (or TP)#A, #B and #C in a predefined format, a field (or bit) for indicatingstate information corresponding to cell-specific (or TP-specific)information associated with specific change-of-use information isadditionally defined in the predefined format in which change-of-useinformation about multiple cells (or TPs) is transmitted. Thereby, UL-DL(re)configuration information about cell (or TP) #A is associated withcell-specific (or TP-specific) information state #0, UL-DL(re)configuration information about cell (or TP) #B is associated withcell-specific (or TP-specific) information state #0, and UL-DL(re)configuration information about cell (or TP) #C is associated withcell-specific (or TP-specific) information state #1.

In FIG. 16, it is assumed that change-of-use information (e.g., achange-of-use indicator) about two cells (TPs) is transmitted through apredefined format and that a base station signals three cell-specific(or TP-specific) information states to a UE. That is, the figureillustrates a case where a plurality of cell-specific (or TP-specific)information states is applied to one change-of-use information item.This case may be interpreted as a case where some cells (or TPs) sharethe same change-of-use information (or UL-DL configuration).

According to another embodiment, UL-DL configuration information may bedesignated for i) each PQI state (PQI field value) and each QLCinformation item, for ii) each PQI state (PQI field value), or for iii)each QCL information.

For example, if change-of-use information (e.g., change-of-useindicators) which the base station signals to the UE is transmitted in afixed resource region on a specific or at a fixed time, large overheadmay be caused to the channel. Further, due to simultaneous transmissionof many pieces of change-of-use information (which may increase, forexample, a coding rate), reliable transmission/reception of thechange-of-use information may not be ensured. In particular, if thechange-of-use information is transmitted as UE-specific informationrather than cell-specific information, the aforementioned problems maybe worsened.

Accordingly, according to this embodiment, change-of-use information(e.g., change-of-use indicators) may be transmitted based on apredefined RNTI in a distributed manner in order to receive i) multiplepredefined resource regions, ii) predefined separate time domains, oriii) the change-of-use information on a specific channel. For example,in the case where change-of-use information through the (E)PDCCH (in theform of, for example, to ensure dynamic change, a newly defined DCIformat or an existing DCI format), all predefined UL-DL configurationcandidates may be arranged such that some candidate information may betransmitted through (E)CCE #A (or (E)CCE set #A), and the othercandidate information may be transmitted (E)CCE #B (or (E)CCE set #B).

If the base station configures multiple EPDCCH sets for the UE, (E)CCE#A and (E)CCE #B may be configured to be present in different EPDCCHsets, or may be configured to be present in one predefined EPDCCH set.Similarly, if the base station configures multiple EPDCCH sets for theUE, (E)CCE set #A and (E)CCE set #B may be configured to be present indifferent EPDCCH sets, or may be configured to be present in onepredefined EPDCCH set. Finally, the UE receives change-of-useinformation by monitoring (E)CCE #A and (E)CCE #B (or (E)CCE set #A and(E)CCE set #B) on the (E)PDCCH.

Further, a resource for receiving change-of-use information (e.g., achange-of-use indicator) on a specific channel may differ between UEs(or UE groups)/cells (or cell groups). Accordingly, the base station maydeliver information about a resource on the specific channel on whicheach UE (or UE group)/cell (or cell group) performs the monitoringoperation (or information about UE/cell grouping) to the UE through apredefined signal (e.g., physical layer or higher layer signal).

In addition, the change-of-use information (e.g., change-of-useindicators) transmitted by the base station may not be normally receivedby the UE due to a bad channel state. In this regard, a response message(e.g., ACK/NACK) for reception of change-of-use information may beadditionally defined. For example, the response message (e.g., ACK/NACK)may be transmitted through an uplink control channel resource (PUCCHresource) linked to resources (e.g., (E)CCE #A and (E)CCE #B) which areused when the UE monitors the change-of-use information on a specificchannel (e.g., (E)PDCCH) be transmitted through an uplink controlchannel resource (PUCCH resource) linked to the lowest index (e.g., thelowest (E)CCE index) among the resources which are used when the UEmonitors change-of-use information on a specific channel (e.g.,(E)PDCCH).

Specifically, if change-of-use information (e.g., change-of-useindicators) is transmitted through L (E)CCEs (wherein, L is a naturalnumber) on the (E)PDCCH, UEs receiving the change-of-use information maybe divided into L groups according to a predefined rule. Herein, the UEsmay be simply divided into L groups based on values obtained byperforming modulo operation on the identifiers (e.g., C-RNTIs) of theUEs using L (namely, based on remainders obtained by dividing theidentifiers of the UEs by L) (i.e., ‘UE group number=(C-RNTI moduloL)’). Alternatively, in consideration of reception of the change-of-useinformation, the UEs may be divided into L groups based on valuesobtained by performing the modulo operation a predefined identifierusing L.

UEs corresponding to individual groups transmit response messages forreception of the change-of-use information through uplink controlchannel resources (PUCCH resources) linked to different (E)CCEsassociated the respective groups. That is, if a UE fails to receive thechange-of-use information, the UE transmits a response message throughan uplink control channel resource (PUCCH resource) linked to a group towhich the UE belongs. For example, if the UE belongs to the K-th group(wherein K is a natural number), the UE may transmit a response messagethrough an uplink control channel resource (PUCCH resource) linked tothe K-th (E)CCE.

Additionally, the response message for reception of the change-of-useinformation (e.g., change-of-use indicator) transmitted by the UE may beconfigured to announce both success/failure (ACK/NACK) of reception ofthe information, or may be configured to announce either failure (NACK)or success (ACK) of reception of the information. For example, in thecase where the UE is configured to announce only failure of reception ofchange-of-use information, the UE may not transmit a response message ifthe information is successfully received, and the base station mayconsider that the UE has successfully received the change-of-useinformation if the base station does not receive a response message fromthe UE (at a specific time or within a specific time interval).

In the case where UEs are configured to announce only failure (NACK) ofreception of change-of-use information, the base station may considerthat all UEs belonging to the K-th group have successfully received thechange-of-use information if the base station does not receive a reposeto failure from any of the UEs on an uplink control channel resource(PUCCH resource) linked to the K-th (E)CCE. Herein, among the UEsbelonging to the K-th group, UEs belonging to a discontinuous reception(DRX) state or a measurement gap may be excluded.

In addition, in the case where change-of-use information (e.g.,change-of-use indicators) is transmitted through a specific channel inpredefined separated time domains, in order to ensure dynamic change,information on some predefined UL-DL configuration candidates may betransmitted through a subframe (e.g., SF #A), and information on theother candidates may be transmitted through another subframe (e.g., SF#B). For example, if cross-carrier scheduling (CCS) is configured in theCA environment according to the aforementioned configuration and thuschange-of-use information about a scheduled cell is transmitted througha specific channel in a scheduling cell (or PCell), overhead to thespecific channel in the scheduling cell (or PCell) may be distributed inthe domain. In addition, the time to receive the change-of-useinformation on the specific channel may be differently defined among UEs(or UE groups)/cells (or cell groups)/TPs (or TP groups).

In addition, a subframe set for monitoring change-of-use information(e.g., change-of-use indicators) of individual UEs may be designated.Herein, information about the subframe set for monitoring change-of-useinformation may be delivered to the UEs by the base station through apredefined signal (e.g., a physical layer or higher layer signal).

Further, subframe sets for monitoring the change-of-use information(e.g., change-of-use indicators) for UEs may be independently (e.g.,differently) designated or only some thereof may be differentlydesignated.

As an additional example, change-of-use information (e.g., achange-of-use indicator) of a predefined specific cell/TP/CC group maybe transmitted in a subframe set (subframe set #A), and change-of-useinformation of the other cells/TPs/CC groups may be transmitted inanother subframe set (subframe set #B). Herein, the base station maydeliver such information to the UEs through a predefined signal (e.g., aphysical layer or higher layer signal).

In addition, if change-of-use information (e.g., a change-of-useindicator) is transmitted based on a predefined RNTI such theinformation is received, a UE may receive the change-of-use informationon a specific channel using the RNTI. Herein, the RNTI defined for thepurpose of reception of the change-of-use information may be set to avalue which is common to all UEs or be differently defined for each UEgroup/cell group. The base station may deliver information about theRNTI to the UE through a predefined signal (e.g., a physical layer orhigher layer signal).

According to an embodiment of the present invention, the cell-specific(or TP-specific) information and/or information about use of subframes(e.g., UL-DL (re)configuration) may be associated with at least one RNTIdefined for the purpose of reception of change-of-use information (e.g.,a change-of-use indicator). If multiple RNTIs are defined for thepurpose of reception of change-of-use information, the RNTIs may beassociated with independent (e.g., different) cell-specific (orTP-specific) information items and/or information items about use ofsubframes, or some of the RNTIs may be defined to be associated with thesame cell-specific (or TP-specific) information items and/or informationitems about uses of subframes. In addition, the base station may deliverinformation about RNTI configurations to the UE though a predefinedsignal (e.g., a physical layer or higher layer signal).

Hereinafter, description will be given of an embodiment of the presentinvention applied in the case where uses for a radio resource aredynamically changed with CA applied.

In the case where uses for a radio resource in a specific cell aredynamically changed with CA applied, embodiments of the presentinvention described above may be applied. However. If use for a radioresource of a specific cell (or CC) is set to be determined through theoperation of monitoring change-of-use information transmitted on thesystem information transmission channel (e.g., PBCH or paging) of thecell, the UE may not efficiently receive SCell-related change-of-useinformation since the UE does not monitor an independent systeminformation transmission channel (e.g., PBCH or paging) for the SCell inthe CA environment regardless of whether or not the CCS technique isapplied.

That is, in the CA environment, the UE monitors a system informationtransmission channel (e.g., PBCH or paging) for the PCell, while systeminformation about the SCell is delivered to the UE by the base stationthrough RRC signaling.

Therefore, according to an embodiment, change-of-use information (e.g.,a change-of-use indicator) about the SCell may be set to be transmittedthrough a MAC signal (or an RRC signal/physical control channel/physicaldata channel) for the SCell in the CA environment. For example,change-of-use information about the PCell may be set to be transmittedthrough a system information transmission channel (e.g., PBCH orpaging), independently of the SCell. This may be interpreted asindependently (e.g., differently) defining the type of a channel forreceiving change-of-use information on the PCell (or scheduling cell)and the type of change-of-use information received on the SCell (orscheduled cell).

If the CCS technique is applied in the CA environment, transmittingchange-of-use information (e.g., change-of-use indicators) about boththe scheduling cell (or PCell) and the scheduled cell (or SCell) througha specific channel at a specific time predefined on the scheduling cell(or PCell) may cause large channel overhead.

In this regard, according to another embodiment of the presentinvention, change-of-use information (e.g., a change-of-use indicator)about the scheduling cell (or PCell) and change-of-use information(e.g., a change-of-use indicator) about the scheduled cell (or SCell)transmitted through a specific channel on the scheduling cell (or PCell)may be set to be independently transmitted through predefined separatedtime domains. For example, if a predefined specific period (i.e., T) is20 ms, the change-of-use information about the scheduling cell (orPCell) may be set to be transmitted in the first subframe time (i.e., SF#n) within the period, and change-of-use information about the scheduledcell (or SCell) may be set to be transmitted in a subframe (i.e., SF#(n+10)) which corresponds to a time 10 ms after the first subframetime. This may be interpreted as applying a predefined time offset value(e.g., Time Offset) between a time at which change-of-use information istransmitted in the scheduling cell (or PCell) and a time at whichchange-of-use information is transmitted in the scheduled cell (orSCell).

Additionally, if the CCS technique is applied in the CA environment,change-of-use information (e.g., a change-of-use indicator) about thescheduled cell may be exceptively transmitted through a specific channelof a specific time in the scheduled cell.

According to an embodiment of the present invention, if the CCStechnique is applied in the CA environment, a subframe time at whichchange-of-use information (e.g., a change-of-use indicator) istransmitted may be differently defined according to respective cells (orCCs) in order to solve the problem of large overhead caused to thespecific channel in the scheduling cell (or PCell) when change-of-useinformation (e.g., change-of-use indicators) about both the schedulingcell (or PCell) and the scheduled cell (or SCell) is transmitted throughthe specific channel.

For example, if the CCS technique is applied in the CA environment, acell (or CC) in which change-of-use information about the schedulingcell (or PCell) and scheduled cell is transmitted may be set to thescheduling cell (or PCell), or individual cells (or CCs) correspondingto respective change-of-use information may be designated.

In addition, a subframe time at which change-of-use information (e.g., achange-of-use indicator) is transmitted may be limited to i) subframesstatically used for downlink use, ii) DL subframes on an SIB, iii) orpredefined specific DL subframes (e.g., a DL subframe set (i.e., SF #0,#1, #5, #6) which cannot be switched to use for transmission ofPSS/SSS/PBCH).

In addition, when some cells perform communication in the same directionor a clustering technique of causing some cells to perform communicationin the same direction is applied in order to attenuate interferenceoccurring due to different communication directions of the cells,change-of-use information items about the cells may be designatedthrough one predefined signal.

In addition, an almost blank subframe (ABS), which is one of eICICtechniques, may be applied in order to attenuate interference occurringdue to different communication directions of the cells. Accordingly,subframe times at which change-of-use information is transmittedaccording to respective cells (or CCs) or a subframe time at which asignal related to change-of-use information about a plurality of cellsmay be defined to have configurability, and the base station maytransmit configurability-related information (e.g., informationindicating whether a specific configuration is applied, informationabout subframe times at which change-of-use information is transmittedaccording to the respective cells (or CCs)) to the UE through apredefined signal.

As an additional embodiment, in the case of NCT (in the CA environment),change-of-use information (e.g., change-of-use indicators) may be set tobe received from the PCell even if a self-scheduling technique isexceptively applied. For example, the base station may transmitchange-of-use information for the NCT to the UE through one of aphysical control channel (e.g., EPDCCH/PDCCH), a physical data channel(e.g., PDSCH), a higher layer signal (e.g., RRC/MAC) and a systeminformation transmission channel (e.g., PBCH/SIB/paging).

According to an embodiment of the present invention, UEs in the IDLEmode may be set to restrictively perform RRM/RLM/CSI measurement for aspecific cell and/or reception of change-of-use information (e.g., achange-of-use indicator) related to the specific cell only in predefinedspecific DL subframes (e.g., a DL subframe set (i.e., SF #0, #1, #5, #6)use of which cannot be changed through transmission of PSS/SSS/PBCH).

According to an embodiment of the present invention, if a UE in the IDLEmode has entered an RRC connected state for a specific cell, but doesnot independently receive change-of-use information (e.g., achange-of-use indicator) from the specific cell, the UE may be set torestrictively perform a monitoring operation related to controlinformation ((E)PDCCH) or reception of data (PDSCH) only in i)predefined specific DL subframes (e.g., a DL subframe set (i.e., SF #0,#1, #5, #6) use of which cannot be changed through transmission ofPSS/SSS/PBCH) or ii) DL subframes on an SIB.

In addition, change-of-use information (e.g., UL-DL (re)configurationinformation) for each cell (or TP) may be signaled through variousembodiments of the present invention described above. For example, toensure RRM/RLM/CSI measurement of the UE according to respective cells(or TPs), some or all non-zero power CSI-RS configuration informationitems for the respective cells (or TPs) may be differently configured.In this context, change-of-use information configuration for therespective TPs (or cells) may be interpreted as meaning thatchange-of-use information is configured according to respective non-zeropower CSI-RS configurations.

Additionally, regarding an interference measurement resource (IMR), if aspecific cell (or TP) uses a subframe of a specific time at which theIMR is configured for UL use, the UE preferably stops interferencemeasurement on the cell (or TP). This is intended to prevent differenttypes (e.g., interference due to UL communication and interference dueto DL communication) of interferences from being aggregated on one IMRto yield an incorrect interference measurement value, considering thatthe interference type varies depending on whether another cell (or TP)uses the specific subframe for UL use or DL use.

Therefore, according to an embodiment of the present invention, i)linkage between non-zero power CSI-RS configuration information and anIMR or ii) linkage between change-of-use information (e.g., UL-DL(re)configuration information) and an IMR may be defined. Herein, thelinkage between non-zero power CSI-RS configuration information and anIMR or linkage between change-of-use information (e.g., UL-DL(re)configuration information) and an IMR may set to be delivered to theUE by the base station through a predefined additional signal (e.g., aphysical layer signal or higher layer signal) or to be implicitlyrecognized based on channel state information process (a CSI process)configuration information, QCL information or PQI information.

For example, in the case where interference measurement is performedbased on the CSI process configuration information, if an IMR linked toa specific CSI process is present in a subframe in which a TP (or cell)corresponding to a non-zero power CSI-RS linked to the CSI process isconfigured for UL use, the UE may exclude a measurement value on the IMRso as not to be used in calculating RI/PMI/CQI in the CSI process suchthat interference measurement is performed only when the TP isconfigured for DL use.

As another example, if interference measurement is performed based onQCL information, each IMR may be connected to at least one non-zeropower CSI-RS. In this case, the QCL information may be considered asindicating QCL between the IMR and the non-zero power CSI-RS. Thereby,the IMR may be considered a valid measurement resource if a TP (or cell)corresponding to the non-zero power CSI-RS connected to an IMR isconfigured for DL use, and may be considered invalid if the TP (or cell)is configured for UL use.

If interference measurement is performed based on PQI information, azero-power CSI-RS appearing in the same PQI state as a non-zero powerCSI-RS linked to a specific TP (or cell) may be recognized in a subframein which the TP is configured for DL use. If the zero-power CSI-RSincludes a resource element (RE) of a specific IMR, measurement may beperformed, considering that the IMR is valid. If all non-zero powerCSI-RSs appearing in the same PQI state as zero-power CSI-RSs includingthe IMR are configured for UL use, the IMR may be considered invalid.

Alternatively, the base station may not apply the implicit ruledescribed above. Instead, the base station may pre-signal an explicitrule. For example, the base station may designate a condition underwhich individual IMRs are valid or invalid for interference measurement.In particular, the condition for validity of interference measurementmay be that each TP (or cell) should be configured for UL use or DL useor that a non-zero power CSI-RS configuration of the TP should beestablished for UL use or DL use. For example, the condition forinterference measurement may be established such that IMR #1 is validwhen TP #1 is configured for DL use, and TP #2 is configured for UL use.

In addition, according to an embodiment of the present invention, thebase station may deliver change-of-use information (e.g., achange-of-use indicator) to the UE (re)using an existing predefinedspecific DCI format.

For example, change-of-use information may be transmitted (re)using DCIformat 3/3A among existing DCI formats. For DCI format 3/3A, the basestation delivers, to a specific UE, RNTI information used in detecting(i.e., blind decoding) DCI format 3/3A and field index informationindicating the position of a field assigned to the specific UE in DCIformat 3/3A through a higher layer signal (e.g., RRC signaling). Whenthe UE receives such information, the UE detects DCI format 3/3A in theCSS and/or acquires the information from the field at a specificposition in DCI format 3/3A. Using the property of DCI format 3/3A, thebase station may configure a specific field (or DCI format) of DCIformat 3/3A for the specific UE through a predefined signal (e.g., ahigher layer signal or physical layer signal) such that use of thespecific field is changed to transmission of change-of-use information.Using a predefined signal, the base station may transmit, to thespecific UE, the following information.

-   -   Field position (or field index) information which is used for        transmission of change-of-use information, not for transmission        of TPC information        -   For example, multiple fields may be configured for            transmission of change-of-use information for the specific            UE. That is, a combination of multiple fields or a            combination of bits in the multiple fields may be            pre-configured such that meaning of change-of-use            information is recognized through the combination.        -   For example, the field used for transmission of            change-of-use information may be used to transmit not only            change-of-use information of the serving cell but also            change-of-use information of a neighboring cell            (participating in cooperative communication).    -   The base station may configure, for the specific UE, a field        used for transmission of TPC information and a field used for        transmission of change-of-use information together.        -   For example, if DCI format 3/3A is detected at any time, the            specific UE may receive the information for the two purposes            (i.e., TPC information, change-of-use information) at the            positions of the predefined fields (serving the respective            purposes).        -   Alternatively, if DCI format 3/3A is detected at any time,            the specific UE may receive the information for the two            purposes (i.e., TPC information, change-of-use information)            at the predefined fields (serving the respective purposes)            simultaneously.    -   If a specific field of DCI format 3/3A is changed to use for        transmission of change-of-use information, DCI format 3/3A may        be transmitted through another predefined search space (e.g., a        USS) or a specific control channel (e.g., EPDCCH) rather than        through the CSS.    -   If a specific field of DCI format 3/3A is changed to use for        transmission of change-of-use information, RNTI information used        in detecting DCI format 3/3A may be assumed as in the case where        DCI format 3/3A is used for the existing purpose (i.e.,        transmission of TPC information) in view of the specific UE.        Alternatively, if DCI format 3/3A is used for the existing        purpose (i.e., transmission of TPC information) in view of the        specific UE, the base station may additionally deliver RNTI        information used in detecting DCI format 3/3A to the UE through        a predefined signal (e.g., a physical layer signal or higher        layer signal) such that the information is differently defined.

According to another embodiment of the present invention, ifchange-of-use information (e.g., a change-of-use indicator) istransmitted through a predefined format (e.g., DCI format 3/3A), CRCbits associated with the format/change-of-use information may beconfigured to be relatively long. By adjusting the length of the CRCbits, the probability of False Alarm of the change-of-use informationmay be reduced. Information about the length/content of the CRC bits maybe delivered to the UE by the base station through a predefined signal(e.g., a higher layer signal or physical layer signal). Additionally,the method and principle described above may be applied to all caseswhere change-of-use information is transmitted through a predefinedformat.

Hereinafter, description will be given of explicit L1 signaling, whichis a technique of signaling for reconfiguration. A group of UEs monitorsa common (E)PDCCH to receive reconfiguration signaling. Accordingly, thecommon search space (CSS) may be selected as a search space for L1signaling. In addition, reliability of the CSS may be low in somesubframes due to inter-cell interferences, but reliable CSS monitoring(detection) needs to be ensured for connectivity of the UE in at leastsome subframes in a cell. A reconfiguration signal needs to betransmitted in only a few subframes (almost once every 10 ms). For thisreason, the CSS may be used.

It addition, it is not preferable to increase only the number of timesof bind decoding in some selected subframes in which a reconfigurationsignal is transmitted. If the reconfiguration signal uses DCI having thesame length as DCI format 0 or DCI format 1C in the CSS, additionalblind decoding may be avoided. In this case, the reconfiguration signalmay be distinguished from the DCIs (i.e., DCI formats 0 and 1C) by usinga different RNTI configured by the base station (eNB).

Accordingly, according to an embodiment of the present invention, L1signaling for UL-DL reconfiguration may be transmitted in the CSS. Theformat of the UL-DL reconfiguration signal may be set to DCI format 0 orDCI format 1C. The eNB may configure, for UEs, RNTIs to be used todecode DCI including UL-DL reconfiguration.

Even if a new DCI is transmitted in the CSS and received by the group ofthe UEs, the content thereof (UL-DL configuration indicated to the UE)does not need to be the same for all UEs. However, the received DCI ispreferably UE-specifically interpreted. This is because UEs may beassociated with different cells when the UEs support CA or CoMP.

In the present invention, in order to UE-specifically interpret a UEgroup common DCI, an extended version of the configuration used in DCIformat 3/3A is applied. That is, even if a group of UEs receives thesame DCI format 3/3A, the respective UEs may derive TPC indicationassociated therewith from different bit positions in the DCI which isreceived in common.

FIG. 17 shows new DCI for UL-DL reconfiguration reflecting theconfiguration described above according to an embodiment of the presentinvention. The DCI may be transmitted including a concatenation ofmultiple UL-DL configurations. Each of the UL-DL configurations may beassociated with a specific cell/TP, and the base station may transmitinformation about the same to the UEs before the new DCI is monitored.Accordingly, each UE may detect the UL-DL configuration of a neighboringcell/TP according to the eNB configuration and the received DCI.

As the aforementioned operation is performed, a UE to which CA isapplied may recognize UL-DL configurations for respective CCs, and an UEto which CoMP is applied may be recognize UL-DL configuration forrespective TPs for CoMP measurement. In addition, a UE fornon-CoMP/non-CA may recognize the UL-DL configuration of a neighboringcell which may be used for CSI measurement.

Accordingly, if multiple cells/TPs have the same UL-DL configuration,UL-DL configurations according to DCI may be associated with themultiple cells/TP.

That is, new DCI for a UL-DL reconfiguration may be transmitted byconcatenating multiple UL-DL configurations, and each of the UL-DLconfigurations may be associated with a specific cell/TP according toconfiguration of the base station. The new DCI for the UL-DLreconfiguration may not be transmitted in all DL subframes. This isbecause the maximum rate for reconfiguration is one transmission per 10ms.

Accordingly, subframes used to transmit the new DCI need to be defined,and the UE should not monitor DL subframes except the defined subframesin order to prevent unnecessary false alarm.

Basically, the UL-DL reconfiguration speed depends on various factorssuch as a backhaul link speed, an adopted ICIC scheme, expected trafficfluctuation and the portion of legacy UEs that are unable to understandthis configuration change.

UL-DL reconfiguration according to L1 signaling may be UE-specificallyestablished for UEs of legacy 3GPP LTE Rel-11. In this case, networkconfigurability is allowed in determining subframes in whichreconfiguration DCI transmitted.

In other words, each eNB may set the period and offset of subframes inwhich new DCI for UL-DL reconfiguration is transmitted. Herein, theperiod may be determined based on reconfiguration speeds considering theaforementioned factors.

The offset may be determined such that transmission of reconfigurationDCI may avoid inter-cell interference. For example, the offset may bedetermined in consideration of ABS configurations of neighboring cells,or be determined such that the offset differs in time from subframes forreconfiguration signals of the neighboring cells.

Regarding reception of a network monitoring and control signal, afterdecoding new DCI for UL-DL reconfiguration, the UE may recognize twodifferently defined UL/DL subframes.

One subframe is a definition according to a UL-DL configuration on oneSIB, and the other one is a UL-DL configuration defined by new DCI.

(E)PDCCH/PDSCH/PUSCH-related operation of the UE may conform toconfiguration defined in the new DCI. For example, the UE may monitor(E)PDCCH and PDSCH only in a special subframe or DL subframe associatedwith a cell/TP and indicated by the new DCI for UL-DL reconfiguration.

Further, the same method may be adopted even in monitoring UL controlinformation (e.g., UL grant). If the DL/special subframe indicated asbeing associated with a cell/TP by the new DCI is scheduled for PUSCHtransmission, the UE may discard detected UL control information. Inthis way, unnecessary false alarm and misbehavior of the UE may beavoided.

It is apparent that the examples/embodiments/method of the presentinvention described above may be included in one of the technicalsolutions proposed in the present invention and be considered as oneembodiment of the present invention. In addition, the embodiments of thepresent invention described above may be independently implemented or acombination or concatenation of some embodiments may be implemented.

In addition, a base station may deliver information on anembodiment/rule/configuration or information on whether or not theembodiment/rule/configuration is adopted, base station to the UE througha predefined signal (e.g., a physical layer or higher layer signal).

Further, embodiments of the present invention may be restrictivelyadopted only when a dynamic change mode for a radio resource is set.

Additionally, in the embodiments described above, QCL information may beinterpreted as “QCL information between a specific reference signal(e.g., DM-RS) used in decoding PDSCH and another predefined referencesignal (e.g., CSI-RS, CRS)” and/or ‘QCL information between a specificreference signal (e.g., DM-RS) used in decoding EPDCCH and anotherpredefined reference signal (e.g., CSI-RS, CRS)”.

It is apparent that an example/embodiment/method given above to describethe present invention may be included as one example and correspond to atechnical solution to the technical problem which the present inventionseeks to solve.

Various embodiments of the present invention described above may beindependently applied. It is apparent that a combination of a part orentirety of at least one embodiment is also included in the technicalsolution proposed in the present invention.

FIG. 18 illustrates a method for receiving DCI according to oneembodiment of the present invention.

Referring to FIG. 18, a UE receives, from a BS, change-of-useinformation about a radio resource, e.g., a change-of-use indicator orDL information related to reconfiguration of a radio resource (S1801).

That is, in step S1801 of FIG. 18, the UE may receive informationrelated to change of use of a radio resource according to one embodimentof the present invention. In step S1801, theinformation/configuration/rule related to change of use/reconfigurationof a radio resource may be configured as described in the embodiments ofthe present invention given above. In some cases, the information may bedetermined by a combination of at least a part of the embodiments of thepresent invention.

In implementing the communication method of the present invention usingCA as described above with reference to FIG. 18, various embodiments ofthe present disclosure described above may be independently applied, ortwo or more of the embodiments may be applied in combination. Forclarity, redundant description will be omitted.

FIG. 19 exemplarily shows a base station and a UE which are applicableto an embodiment of the present invention. If a relay is included in awireless communication system, communication on the backhaul link may beperformed between the base station and the relay, and communication onthe access link is performed between the relay and the UE. Accordingly,the base station or UE illustrated in the figure may be replaced withthe relay according to a situation.

Referring to FIG. 19, a wireless communication system includes a BS 1910and a UE 1920. The BS 1910 includes a processor 1912, a memory 1914 anda radio frequency (RF) unit 1916. The processor 1912 may be configuredto implement the procedures and/or methods proposed in the presentinvention. The memory 1914 is connected to the processor 1912 and storesvarious kinds information related to operation of the processor 1912.The RF unit 1916 is connected to the processor 1912, and transmitsand/or receives a radio signal. The UE 1920 includes a processor 1922, amemory 1924 and an RF unit 1926. The processor 1922 may be configured toimplement the procedures and/or methods proposed in the presentinvention. The memory 1924 is connected to the processor 1922 and storesvarious kinds information related to operation of the processor 1922.The RF unit 1926 is connected to the processor 1922, and transmitsand/or receives a radio signal. The BS 1910 and/or the UE 1920 may havea single antenna or multiple antennas.

The embodiments described above are constructed by combining elementsand features of the present invention in a predetermined form. Eachelement or feature should be understood as optional unless explicitlymentioned otherwise. Each of the elements or features can be implementedwithout being combined with other elements. In addition, some elementsand/or features may be combined to configure an embodiment of thepresent invention. The sequence of the operations discussed in theembodiments of the present invention may be changed. Some elements orfeatures of one embodiment may also be included in another embodiment,or may be replaced by corresponding elements or features of anotherembodiment. Claims that are not explicitly cited in each other in theappended claims may be combined to establish an embodiment of thepresent invention or be included in a new claim by subsequent amendmentafter the application is filed.

Embodiments of the present invention may be implemented by various meanssuch as, for example, hardware, firmware, software, or combinationsthereof. When practiced in hardware, one embodiment of the presentinvention may be implemented by one or more ASICs (application specificintegrated circuits), DSPs (digital signal processors), DSPDs (digitalsignal processing devices), PLDs (programmable logic devices), FPGAs(field programmable gate arrays), processors, controllers,microcontrollers, microprocessors, and the like.

When practiced in firmware or software, an embodiment of the presentinvention may be implemented in the form of a module, a procedure, afunction, or the like which performs the functions or operationsdescribed above. Software code may be stored in the memory unit andexecuted by the processor. The memory unit may be disposed inside oroutside the processor to transceive data with the processor via variouswell-known means.

The present invention may be carried out in other specific ways thanthose set forth herein without departing from the characteristics of thepresent invention. Therefore, the above embodiments should be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, and all changes coming within the meaning and equivalencyrange of the appended claims are intended to be embraced therein.

INDUSTRIAL APPLICABILITY

A method for receiving downlink control information in a wirelesscommunication system and an apparatus for the same have been describedabove, focusing on a case where the present invention is applied to a3GPP LTE system. The present invention may also be applied to variouswireless communication systems other than the 3GPP LTE system.

1. A method for receiving control information by a user equipment (UE)in a wireless communication system, comprising: receivingreconfiguration downlink control information (reconfiguration DCI),wherein the reconfiguration DCI comprises a plurality ofreconfigurations related with a UE group comprising the UE, and is setto be received based on a radio network temporary identifier (RNTI)defined for the reconfiguration DCI.
 2. The method according to claim 1,wherein the reconfiguration DCI is set to be transmitted through acommon search space (CSS) of a primary cell (PCell).
 3. The methodaccording to claim 1, wherein the RNTI defined for the reconfigurationDCI is identically configured for the UE group.
 4. The method accordingto claim 3, wherein the RNTI defined for the reconfiguration DCI isconfigured through UE-specific radio resource control (RRC) signaling.5. The method according to claim 1, wherein, when the number of bits forthe plurality of reconfigurations is less than the number of bitsconstituting the reconfiguration DCI, unused bits of the bitsconstituting the reconfiguration DCI are set to a specific value.
 6. Themethod according to claim 5, wherein the specific value is considered asa virtual cyclic redundancy check (virtual CRC) by the UE.
 7. The methodaccording to claim 5, wherein the number of the reconfigurations isindicated through higher layer signaling or physical layer signaling. 8.The method according to claim 5, wherein the number of bits constitutingthe reconfiguration DCI is indicated through higher layer signaling orphysical layer signaling.
 9. The method according to claim 5, whereinlocations of the reconfigurations are set to differ from each other. 10.The method according to claim 9, wherein information about the locationsof the reconfigurations is indicated through UE-specific signaling. 11.A user equipment for receiving control information in a wirelesscommunication system, comprising: a radio frequency unit; and aprocessor, wherein the processor is configured to receivereconfiguration downlink control information (reconfiguration DCI),wherein the reconfiguration DCI comprises a plurality ofreconfigurations related with a UE group comprising the UE, and is setto be received based on a radio network temporary identifier (RNTI)defined for the reconfiguration DCI.